http://www.foxnews.com/world/2010/10/29/north-korea-opens-south-korea/
*facepalm*
Theoretically it is possible, but I doubt it.
Prior to Cheonan incident, Lee has been working hard to arrange another Inter-Korean Summit, and was eager to reap political dividend from it. Chia Head screwed him badly.
As for G-20 Summit, he guy basically volunteered to be blackmailed by hosting it.
The guy is always up for cheap political PR, eager to make him look good, whatever the consequence is.